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POGet the MappingResult firstObject value within the Persistent Storage to avoid "Illegal attempt to establish relationships" errors
 

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    <p>I am fetching an object from the <code>persistentStoreManagedObjectContext</code> and showing some of its value to my user within a UIView. That object, let's call it <code>Book</code> has an <code>Author</code> relationship. Whenever I am about to display that book, I check if the author is set or not. If it's not set, I do:</p> <pre><code> [[RKObjectManager sharedManager] getObjectsAtPath:[NSString stringWithFormat:@"/api/rest/userprofiles/%@/",_currentBook.authorID] parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {..} </code></pre> <p>Within the success callback, I want to do a:</p> <pre><code> _currentBook.author = mappingResult.firstObject; if (![_currentBook.managedObjectContext saveToPersistentStore:&amp;error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); } </code></pre> <p>However, I can't do <code>_currentBook.author = mappingResult.firstObject;</code> because I get:</p> <pre><code>Illegal attempt to establish a relationship between objects in different contexts </code></pre> <p>However, I know that this newly fetched <code>Author</code> is saved within the persistentStoreCoordinator, because I configured my RestKit to do so (or it's by default, I can't remember). So I don't want to create that object AGAIN, I would just want to get it's value within my currentContext which is <code>persistentStoreManagedObjectContext</code>. Do I have to use a NSFetchedResultsController just for that?</p> <p><strong>Edit</strong></p> <p>I already have a connection in the book to connect to the author, via the authorID, which I send back at the same time as getting the Book object from my server. However, it might be the case that the Author Object is not fetched yet, hence I keep that ID.</p> <pre><code>[bookMapping addConnectionForRelationship:@"author" connectedBy:@{ @"authorID": @"identifier" }]; </code></pre> <p>However, even after that author is fetched, book.author is set to null, unless I REFETCH once again in the persistent storage.</p>
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